1. Field of the Invention
The present invention relates to a method of sensing failure of a thermostat in a vehicle, and more particularly, to a method of sensing failure of the thermostat in the vehicle to previously prevent overheat of an engine in the vehicle by sensing the failure of the thermostat which opens and closes a coolant passage depending on the temperature of the coolant for cooling the engine.
2. Description of the Prior Art
Generally, a vehicle is provided with a cooling system for cooling the engine to keep the temperature of the engine suitable while the vehicle is traveling. The cooling system is classified into an air cooling type using air and a water cooling type using water, depending on the cooling method. The cooling system circulates air or water naturally or forcibly and cools the engine.
In the case of the cooling system using the coolant (cooling water) among them, on an outlet portion of a water jacket formed between a cylinder block and a cylinder head of an engine, a thermostat which suitably adjusts the temperature of the coolant flowing coolant passages is mounted.
Therefore, the thermostat is closed and prevents the coolant from flowing into a radiator when the temperature of the coolant is below a normal temperature. As the temperature of the coolant becomes closer to the normal temperature, the thermostat begins to gradually open. When it reaches the normal temperature, the thermostat fully opens to permit the coolant to flow into the radiator, thereby adjusting the temperature of the coolant and cooling the engine.
A thermostat includes a bellows type and a pellet type. For the bellows type thermostat, the bellows made of thin metal plate and a valve are assembled and volatile liquid, such as alcohol, is hermetically contained in the bellows. The coolant passage is configured to be opened and closed by the elongation and compression of the bellows due to the expansion and contraction of the hermetically contained liquid according to the temperature of the coolant.
For the pellet type thermostat, the thermostat comprises a shaft attached to a case, and a valve and a spring installed on a small cylinder. Wax and synthetic rubber are hermetically contained in the cylinder. When the temperature rises, a membrane made of synthetic rubber is compressed by expansion of wax and in turn, the cylinder urges the spring and is lowered to open the valve. When the temperature lowers, since liquid wax is solidified and contracted, the rubber membrane returns to an original position and the valve is closed. By such opening and closing operation, the coolant is circulated and cools the engine.
As described above, the thermostat effectuates the operation of cooling the engine while opening and closing the valve by expansion and contraction of the hermetically contained liquid according to the temperature of coolant. Thus, if malfunction sometimes occurs upon opening and closing the valve due to inferiority, defects and deteriorated durability of parts, normal cooling operation is not carried out and thus, the engine is overheated. Further, the overheat of the engine causes deformation of each of parts and even damage of the engine as well as knocking or pre-ignition in the combustion state in the engine. As a result, there is a problem that the power of the engine lowers.